After all the mails and lots of opinions on this matter, I think it's important not to lose the thread and remember that The timing problems we've been talking about, resides in the sound module of the JV/XP itself and are due to bad processor power.
It has nothing to do with: Midi slowdowns or hardware/software sequencer problems. (which are more specific to the XP-50,60 and 80,-but that's another sad story...!!)

So there's nothing we can do about it!
Only the constructers -the japanese Roland- can fix this...but I don't think they will, as long as there is people buying these modules; and as long as there is people saying they are OK, too.

There might be some people who's satisfied and accept these synths for being 10- or maybe 20-voice modules and not 64.That's up to them and it's OK with me, but I can't accept it myself.
I bought mine as a unit with 64 simultaneous polyphonic notes and nothing else. Besides- 64 "healthy" voices!!Not sick ones!!

Calling up Roland and complaining about it, it's no use. They'll always turn you down and tell some kind of a story-bla, bla...
So I did following instead: I put some examples of the timing errors on a disk and sent it to Roland.
These examples were so perfect and clear that Roland could do nothing but recognize that the "blistering speed processor" (as they call it) was really bad.

But recognizing the problem didn't help me att all!!
What I mean is that they should fix it so I can use the 64-voices I've payed for.

I recommend anyone who is discontent with these products to claim that too.
Only by warning people for these defects, and by massive complaints can we make Roland do something about it.

Finally- it's hard to believe that these fantastic modules have such a miserable defect.

PS. 1- I was about to write that the ROM version won't help the problem, but I can read it already on the last mails!
2- I find Tottys reflections, about the 2080 being slower than the 1080, very wise.
I might as well say that Roland itself recognized (besides admiting the defects on the JV/XP series) that the 2080 was slower than the 1080.